1 /* 2 Example of instantiating of the WebAssembly module and invoking its exported 3 function. 4 5 You can compile and run this example on Linux with: 6 7 cargo build --release -p wasmtime-c-api 8 cc examples/fuel.c \ 9 -I crates/c-api/include \ 10 target/release/libwasmtime.a \ 11 -lpthread -ldl -lm \ 12 -o fuel 13 ./fuel 14 15 Note that on Windows and macOS the command will be similar, but you'll need 16 to tweak the `-lpthread` and such annotations. 17 18 You can also build using cmake: 19 20 mkdir build && cd build && cmake .. && cmake --build . --target wasmtime-fuel 21 */ 22 23 #include <assert.h> 24 #include <stdio.h> 25 #include <stdlib.h> 26 #include <wasm.h> 27 #include <wasmtime.h> 28 29 static void exit_with_error(const char *message, wasmtime_error_t *error, 30 wasm_trap_t *trap); 31 32 int main() { 33 wasmtime_error_t *error = NULL; 34 35 wasm_config_t *config = wasm_config_new(); 36 assert(config != NULL); 37 wasmtime_config_consume_fuel_set(config, true); 38 39 // Create an *engine*, which is a compilation context, with our configured 40 // options. 41 wasm_engine_t *engine = wasm_engine_new_with_config(config); 42 assert(engine != NULL); 43 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL); 44 assert(store != NULL); 45 wasmtime_context_t *context = wasmtime_store_context(store); 46 47 error = wasmtime_context_set_fuel(context, 10000); 48 if (error != NULL) 49 exit_with_error("failed to set fuel", error, NULL); 50 51 // Load our input file to parse it next 52 FILE *file = fopen("examples/fuel.wat", "r"); 53 if (!file) { 54 printf("> Error loading file!\n"); 55 return 1; 56 } 57 fseek(file, 0L, SEEK_END); 58 size_t file_size = ftell(file); 59 fseek(file, 0L, SEEK_SET); 60 wasm_byte_vec_t wat; 61 wasm_byte_vec_new_uninitialized(&wat, file_size); 62 if (fread(wat.data, file_size, 1, file) != 1) { 63 printf("> Error loading module!\n"); 64 return 1; 65 } 66 fclose(file); 67 68 // Parse the wat into the binary wasm format 69 wasm_byte_vec_t wasm; 70 error = wasmtime_wat2wasm(wat.data, wat.size, &wasm); 71 if (error != NULL) 72 exit_with_error("failed to parse wat", error, NULL); 73 wasm_byte_vec_delete(&wat); 74 75 // Compile and instantiate our module 76 wasmtime_module_t *module = NULL; 77 error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module); 78 if (module == NULL) 79 exit_with_error("failed to compile module", error, NULL); 80 wasm_byte_vec_delete(&wasm); 81 82 wasm_trap_t *trap = NULL; 83 wasmtime_instance_t instance; 84 error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap); 85 if (error != NULL || trap != NULL) 86 exit_with_error("failed to instantiate", error, trap); 87 88 // Lookup our `fibonacci` export function 89 wasmtime_extern_t fib; 90 bool ok = wasmtime_instance_export_get(context, &instance, "fibonacci", 91 strlen("fibonacci"), &fib); 92 assert(ok); 93 assert(fib.kind == WASMTIME_EXTERN_FUNC); 94 95 // Call it repeatedly until it fails 96 for (int n = 1;; n++) { 97 uint64_t fuel_before; 98 wasmtime_context_get_fuel(context, &fuel_before); 99 wasmtime_val_t params[1]; 100 params[0].kind = WASMTIME_I32; 101 params[0].of.i32 = n; 102 wasmtime_val_t results[1]; 103 error = 104 wasmtime_func_call(context, &fib.of.func, params, 1, results, 1, &trap); 105 if (error != NULL || trap != NULL) { 106 if (trap != NULL) { 107 wasmtime_trap_code_t code; 108 assert(wasmtime_trap_code(trap, &code)); 109 assert(code == WASMTIME_TRAP_CODE_OUT_OF_FUEL); 110 } 111 printf("Exhausted fuel computing fib(%d)\n", n); 112 break; 113 } 114 115 uint64_t fuel_after; 116 wasmtime_context_get_fuel(context, &fuel_after); 117 assert(results[0].kind == WASMTIME_I32); 118 printf("fib(%d) = %d [consumed %lu fuel]\n", n, results[0].of.i32, 119 fuel_after - fuel_before); 120 121 error = wasmtime_context_set_fuel(context, 10000); 122 if (error != NULL) 123 exit_with_error("failed to set fuel", error, NULL); 124 } 125 126 // Clean up after ourselves at this point 127 wasmtime_module_delete(module); 128 wasmtime_store_delete(store); 129 wasm_engine_delete(engine); 130 return 0; 131 } 132 133 static void exit_with_error(const char *message, wasmtime_error_t *error, 134 wasm_trap_t *trap) { 135 fprintf(stderr, "error: %s\n", message); 136 wasm_byte_vec_t error_message; 137 if (error != NULL) { 138 wasmtime_error_message(error, &error_message); 139 } else { 140 wasm_trap_message(trap, &error_message); 141 } 142 fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data); 143 wasm_byte_vec_delete(&error_message); 144 exit(1); 145 } 146